Thorium test begins

21 June 2013

Thorium fuel is now being tested in the Halden research reactor in Norway. It was loaded in the last week of April, defining the start of a physical test program that will simulate how it operates in a power reactor.

Led by Norwegian company Thor Energy, the test will provide unique information necessary for qualifying this new fuel material for commercial use in current reactors.

The thorium fuel is in the form of pellets composed of a dense thorium oxide ceramic matrix containing about 10% of finely blended plutonium oxide as a 'fissile driver'. As a mixed-oxide (MOX) fuel variant it is familiar to the nuclear industry, but thorium-MOX fuel has certain advantages compared to the uranium-MOX fuels in use at some reactors around the world. It promises higher operating safety margins due to higher thermal conductivity and melting point, and produces no new plutonium as it operates. Thor Energy pointed out that thorium-plutonium fuels therefore provide a new option for reducing civil and military plutonium stocks.

Close up with one of the test fuel pellets (Image: Thor Energy)

Company CEO Oystein Asphjell said the trial was was "the beginning of a new era - not only for our company and our partners, but as an important evolutionary step in the nuclear power industry."

The irradiation test will run for around five years after which the fuel will be studied to quantify its operational performance and gather data to support the safety case for its eventual use in commercial reactors. Areas for study include a range of chemical and physical changes in the fuel related to high temperatures, neutron flux, interations with fuel cladding and changes in ceramic structure.

Engineers atop the Halden reactor (Image: Thor Energy / T Tandberg)

The eight pellets for this experiment were made by the European Commission's Institute for Transuranium Elements in Germany, part of the Joint Research Centre. The next phase of test pellets will be made in Norway and the subsequent 'fully proto-typical pellets' will be made by the UK's National Nuclear Laboratory.

When qualified, thorium-plutonium mixed-oxide fuel could be used in a wide range of today's commercial nuclear power plants and so would offer another fuel option for the nuclear industry.

Other approaches to begin using thorium include a research program by Candu of Canada and China National Nuclear Corporation to develop a version of the Candu design that could use thorium fuel as well as recycled uranium. Indian planners are moving towards a complex three-stage program to use natural uranium and then fast-neutron reactors to create uranium and plutonium drivers for a third stage powered by thorium.